I just took ownership of a 99 xt350 from my brother, and although it was well taken care of I have learned that the valves have never been adjusted. it has 4000miles and runs strong even at highway speeds of 70mph+. I have always rode 2 strokers except for a 04 wr450f (stolen 3wks into having it) Im unsure how often valves should be adjusted. The local yamaha shop is trying to charge $350. CRAZY!!!! Is it a do it yourself kind of job? if not whats a fair price to pay to have it done? How do i even know if they need adjusting? Any help would be great. Thanks.